Years ago we got a postcard from a friend who was vacationing in Key West, Fla. On the front of the card was a recipe for Key Lime Pie that was different than other recipes we’d seen. In addition to the usual lime juice, condensed milk and egg yolks, beaten egg whites were folded into the filling. It wasn’t much of a change, but we liked the idea, and it gave us something to do with the leftover whites. We tweaked the recipe by adding a couple of tablespoons of sugar and an extra white, and it was so delicious, we’ve never tried it any other way.

The recipe for key lime pie could be right out of a cookbook for dummies. It’s ridiculously easy; if you can handle a whisk and turn on a mixer, you can put together a dessert that makes people swoon. Because the filling contains eggs, we like to give it some baking time, but there are versions that never get near an oven. The cooking, if you can call it that, starts in the mixing bowl when the lime juice combines with the egg yolks and sweetened condensed milk. The acid in the limes causes the proteins in the yolks and condensed milk to bond together and set the filling.

Key lime pies were first made more than 150 years ago in Florida when someone got the idea of combining lime juice with sweetened condensed milk and pouring the mixture into a pastry crust. Over the years, graham cracker crusts have replaced the pastry; the crisp crumbs are a perfect match with the soft, creamy filling. It’s important to use fresh limes, but not necessarily key limes. Very few key limes ever make it to market, and experienced tasters say supermarket Persian limes are as good as the real thing and make a great pie.